It is known in the prior art that when mutual inductance exists between groups of windings in an AC rotary machine having a plurality of groups of windings, currents of the respective groups of windings are affected by the currents of the other groups of windings, leading to an increase in the likelihood of current, voltage, and torque oscillation.
Hence, an AC motor control apparatus that includes a plurality of inverters and suppresses interference caused by mutual inductance between a plurality of groups of windings (i.e. realizes non-interference) by controlling an average current and a differential current of the respective inverters has been proposed (see PTL 1, for example).
More specifically, in this AC motor control apparatus, a current imbalance is reduced by determining an average voltage command on the basis of a deviation between an average value (an average current) of respective output currents of the inverters and an average current command in a rotational two-axis coordinate system, determining a differential voltage command on the basis of a deviation between a difference (a differential current) between the respective output currents of the inverters and a differential current command, returning the average voltage command and the differential voltage command to voltage commands for the respective groups of windings, and outputting the commands.
A control apparatus for a three-phase rotary machine that includes a plurality of inverters and prevents an overcurrent from flowing through a system that is operating normally when one system breaks down so that a current cannot be passed therethrough by controlling a control gain ratio between a sum current and a differential current of the respective inverters in accordance with a reference frequency has also been proposed (see PTL 2, for example).